It is known that turbochargers have previously been provided in internal combustion engines of automobiles or the like for purposes of achieving enhanced output. A turbocharger has a turbine scroll into which the exhaust of an internal combustion engine is fed, a turbine impeller which is rotated by supplying the exhaust (fluid) in the turbine scroll via a conduit, a compressor impeller which is integrally rotated with the turbine impeller, and a compressor scroll as a diffuser which is supplied with the air (fluid) from the compressor impeller via a conduit, wherein the pressurized air from the compressor scroll is forcibly supplied to a combustion chamber of the internal combustion engine.
For purposes of rectifying the flow of fluid, vanes may be provided in either or both of the conduit through which exhaust flows on the aforementioned turbine side and the conduit through which air flows on the compressor side.
The vanes provided in the conduit on the turbine side are described as follows. With respect to the exhaust which is fed to the turbine impeller and whose flow rate is increased by the turbine scroll formed in the turbine housing, there is uniform inflow from the periphery of the turbine impeller due to vanes, achieving enhanced turbine efficiency. With respect to such vanes, there is known to be a fixed vane-type in which the vanes are fixed to one of the mutually opposing front faces of the turbine housing or the bearing housing, and a variable vane-type in which shafts provided in the respective vanes between the aforementioned mutually opposing front faces of the turbine housing and the bearing housing are provided so as to be simultaneously rotated by a link mechanism or the like, changing the angles of the vanes in unison.
With the fixed vane-type, since the exhaust inflow angle is fixed, it is impossible to vary the exhaust flow rate according to the rotational frequency or the like of the internal combustion engine. In contrast, with the variable vane-type, the exhaust flow rate can be varied by changing the exhaust inflow angle according to the rotational frequency or the like of the internal combustion engine. On the other hand, in contrast to the relatively simple configuration of the fixed vane-type, the variable vane-type has a complex configuration, because it has moving parts.
Furthermore, there is the problem that an interstice called a vane side clearance arises with respect to the vanes that are provided between the aforementioned mutually opposed front faces of the turbine housing and the bearing housing. That is, even if the clearance between the vanes and the opposing turbine housing or bearing housing is designed to be zero, it is extremely difficult to actually keep the clearance at zero, because the turbine housing that has a complex form experiences uneven thermal deformation during operation, and deformation also occurs due to differences in thermal expansion from the different materials of the vanes and the bearing housing to which the vanes are fixed.
Here, in contrast to the variable vane-type where it is necessary to provide a given side clearance on both sides of the vanes due to the moving parts, a side clearance only occurs on one side of the vanes in the fixed vane-type.
With respect also to vanes provided in the conduit on the compressor side, a side clearance similarly arises, even though the temperature is lower compared to the turbine.
As prior art reference information for such turbochargers in relation to the present invention, for example, there is a case in which both fixed vanes and variable vanes are provided (see Patent Document 1 and the like). In addition, there is also a case pertaining to variable vanes where the vanes are interposed in a turnable manner between a rear exhaust inlet wall and a front exhaust inlet wall, wherein side clearance between the rear exhaust inlet wall side and the vanes is reduced by providing a pressing means between the respective vane shafts and the bearing housing which presses the respective shafts toward the rear exhaust inlet wall side, causing displacement of the vanes toward the rear exhaust inlet wall side (see Patent Document 2 and the like).